The present invention is directed to creating optical systems on a wafer level, including bonding at least two dies together. In particular, the present invention is directed efficient creation of optical systems, particularly the efficient provision of bonding material of a controlled height, the final individual module having at least two bonded dies.
As the demand for smaller optical components to be used in a wider variety of applications increases, the ability to efficiently produce such optical elements also increases. In forming optical elements at a mass production level, the need for accurate alignment increases. Such alignment is even more critical when integrating more than one optical element. As used herein, optical elements is to include passive optical elements, such as diffractive lenses, refractive lenses, beam splitters, rotators, mirrors, i.e., elements which affect light incident thereon, as well as active optical elements, which create light or which have physical characteristics thereof modified in response to light.
To achieve greater alignment tolerances, passive alignment techniques have been used as set forth in U.S. Pat. No. 5,638,469 to Feldman entitled xe2x80x9cMicroelectronic Module Having Optical and Electrical Interconnectsxe2x80x9d. One such passive alignment technique is to place metal pads on the optics and on the laser and place solder between them and use self-alignment properties to achieve the alignment. When solder reflows, surface tension therein causes the parts to self-align. However, passive alignment has not been employed for wafer-to-wafer alignment. In particular, the high density of solder bumps required and the thickness and mass of the wafer make such alignment impractical.
Another problem in wafer level production of optical elements including bonding at least two wafers arises due to the dicing process for forming the individual integrated elements. The dicing process is messy due to the use of a dicing slurry. When single wafers are diced, the surfaces thereof may be cleaned to remove the dicing slurry. However, when the wafers are bonded together, the slurry enters the gap between the wafers. Removing the slurry from the gap formed between the wafers is quite difficult.
Passive optical elements themselves may be formed photolithographically, as set forth, for example, in U.S. Pat. No. 5,218,471 to Swanson et al. entitled xe2x80x9cHigh-efficiency, Multilevel, Diffractive Optical Elementsxe2x80x9d. The passive optical elements may also be formed by injection molding, as set forth, for example, in U.S. Pat. No. 5,728,324 to Welch et al. entitled xe2x80x9cMolding Diffractive Optical Elementsxe2x80x9d. Further, the passive optical elements may be made by replicating on a wafer level, as set forth, for example, in U.S. Pat. No. 6,027,595 to Suleski et al. entitled xe2x80x9cMethod of Making Optical Replicas by Stamping in Photoresist and Replicas Made Therebyxe2x80x9d. More expensive passive optical elements, such as etalons, and many active optical elements, are more typically diced prior to integration, although some active optical elements, such as the power monitor disclosed in commonly assigned co-pending U.S. patent application Ser. No. 09/548,018 to Morris et al., entitled xe2x80x9cTransmission Detection for Vertical Cavity Surface Emitting Laser Power Monitor and Systemxe2x80x9d, may also be formed and bonded on the wafer level.
Considering the foregoing background, it is an object of the present invention to efficiently produce optical elements including bonding of at least two dies. In accordance with the present invention, this may be realized by simultaneously providing bonding material.
These and other objects of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description gives specific examples, while indicating the preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.